Use of Vinca Alkaloids and Salts Thereof

ABSTRACT

An agent containing a vinca alkaloid or its pharmacologically acceptable salt as an active ingredient can induce insulin production and/or secretion of non-neoplastic cells derived from the pancreas.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese Patent Application No. 2003-13125, filed on May 9, 2003 and Japanese Patent Application No. 2003-373665, filed on Oct. 31, 2003, both of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the use of vinca alkaloids and their salts. More specifically, the present invention relates to agents that enhance insulin-producing and/or -secreting abilities of non-neoplastic cells derived from the pancreas, therapeutic agents for diabetes, blood glucose level-lowering agents, methods for inducing differentiation of non-neoplastic cells derived from the pancreas, methods for enhancing insulin-producing and/or -secreting abilities of non-neoplastic cells derived from the pancreas, methods for producing pancreas-derived non-neoplastic cells whose insulin-producing ability has been enhanced, methods for culturing non-neoplastic cells derived from the pancreas, methods for producing insulin, pancreas-derived non-neoplastic cells that have been induced to differentiate, and pancreas-derived non-neoplastic cells whose insulin-producing and/or -secreting abilities have been enhanced.

BACKGROUND ART

Diabetes is a disease arising from shortage of blood insulin and impaired insulin function, resulting in increased blood glucose concentrations, accompanied by complications such as neuropathy, visual disturbance, renal damage, etc. About 7 million people are afflicted with diabetes in Japan alone. There are two major types of diabetes: Type 1 diabetes is caused by an autoimmune destruction of insulin-producing pancreatic β cells, resulting in an absolute lack of insulin. On the other hand, type 2 diabetes is caused by the expression of insulin resistance in target tissues, such as muscle, fat, and liver, or by a decrease in blood insulin levels due to a decline in pancreatic β cell function. Thus, it can be said that both type 1 and type 2 result from impaired pancreatic β-cell function.

For treatment of type 1 diabetes, insulin injections are conventionally used to lower blood glucose levels in most cases. It is needless to say that, in such cases, four injections a day are laborious to patients. For treatment of type 2, the PPARγ inhibitor, which reduces insulin resistance, is used in some cases. However, the inhibitor is not very effective and causes obesity as a side effect, as has been pointed out. In other cases, agents such as sulfonylurea, which promotes insulin release from β cells, are used, but they are also not very effective.

Apart from drug dependent treatment, a new treatment by transplantation of cells or tissue has been considered promising as regenerative therapy. If large amounts of cells with insulin-releasing ability can be transplanted into type I diabetes patients, four insulin injections per day can be avoided for a long term. Meanwhile, transplantation of insulin-releasing cells is also effective for type 2 diabetes because, irrespective of insulin resistance in target tissues, normal insulin production supresses the increase of blood glucose level. It is expected that the efficacy of transplantation is far superior to that of treatment with agents currently used, e.g., sulfonylurea, that induce insulin release from β cells.

Porcine pancreatic cells are expected to be utilized in regenerative therapy for diabetes because of their ease of availability, immunological properties, etc. The technique for collecting large amounts of cells and inducing them to differentiate into insulin producing and releasing cells to a sufficient degree has never been known in any cell system.

Most of pancreatic β cells are generated in the fetal period and then proliferate and differentiate very slowly (Herrera, P. L. et al., Development 127: 2317-2322 (2000)). However, experiments have shown that when the pancreas is damaged β cells actively differentiate and proliferate. Differentiation and proliferation of β cells, together with growth of remnant β cells, occur from pancreatic ductal cells both in adult mice subjected to a 90% partial pancreatectomy and in mice that have developed impaired glucose tolerance due to β cell destruction induced by alloxan. These findings have revealed that stem cells are also present in the adult pancreas and have regenerative capacity (Bonner-Wier S. et al., Diabetes 42: 1715-1720 (2000)). Thus, experiments were performed in which stem cells were isolated from the pancreatic ducts and induced to differentiate into insulin-producing cells (Ramiya, V. K. et al., Nature Med. 6: 278-282 (2000) and Bonner-Weir, S. et al., Proc. Nat. Acad. Sci. USA 97: 7999-800 (2000)). Still, a marker of pancreatic stem cells was not known. It was reported last year that nestin, a marker expressed in neural precursor cells, is a marker of pancreatic stem cells, and nestin was confirmed to be expressed in adult pancreatic duct. (Hunziker, E. et al., Biochem. Biophys. Res. Commun. 271: 116-119 (2000)). Furthermore, in vitro culture and differentiation into cells with phenotype including that of insulin-producing cells was succeeded (Zulewski, H. et al., Diabetes 50: 521-533 (2001)). In addition, differentiation of ES cells into pancreatic inlet-like tissues was also succeeded (Lumelysky, N. et al., Science 292: 1389-1394 (2001)). These techniques are expected to be clinically applied in regenerative medicine of the pancreas.

While studies are under way on cells that can potentially serve as materials for pancreatic β cells, physiologically active substances that induce differentiation of pancreatic β cells are considered promising for clinical application in the field of regenerative medicine. Examples of substances that have thus far been known as inducers of differentiation into β cells include activin A, which belongs to the TGF-β superfamily (Demeterco, C. J. et al., Clin. Endo. 85: 3892-3897 (2000)); betacellulin (BTC), which belongs to the EGF family (Ishiyama, N. et al., Diabetologia 41: 623-628 (1998) and Yamamoto, K. et al., Diabetes 49: 2021-2027 (2000); hepatocyte growth factor (HGF) (Ocana, A. G. et al., J. Bio. Chem. 275: 1226-1232(2000)); basic fibroblast growth factor (bFGF) (Assady, S. et al., Diabetes 50: 1691-1697 (2001)); etc. These substances are proteins, which are not suitable for oral administration. Further, it is difficult to introduce such substances by means of injection because of their immunological problem and instability.

Meanwhile, it has been reported that among low-molecular-weight compounds, nicotinamide acts as a poly (ADP-ribose) synthetase inhibitor, promoting regeneration of pancreatic β cells (Watanabe, T. et al., Proc. Natl. Acad. Sci. USA 91: 3589-3592 (1994) and Sjoholm, A. et al., Endocrinology 135: 1559-1565 (1994)). In addition, nicotinamide has also been reported to promote the expression of Reg protein (Watanabe, T. et al., Proc. Natl. Acad. Sci. USA 91: 3589-3592 (1994)), which promotes the proliferation and differentiation of pancreatic β cells (Akiyama, T. et al., Proc. Natl. Acad. Sci. USA 98: 48-53 (2001)). In another report, fetal porcine pancreatic islet-like cell clusters (ICCs) were induced to differentiate into insulin-producing cells using sodium butyrate and dexamethasone(Korsgren, O. et al., Ups J. Med. Sci. 98: 39-52 (1993)), but the technology is less likely to be put into practical use because of the low specificity.

Meanwhile, the structures of conophylline (Umezawa, K. et al., Anticancer Res. 14: 2413-2418 (1994)) and conophyllidine (Kam, T. S. et al., J. Nat. Prod. 56: 1865-1871 (1993)), both of which are alkaloids isolated from leaves of an Apocynaceae family plant grown in Malaysia and Thailand are known, as shown in FIG. 1. Conophylline is known to exhibit anti-tumor activity in animals (Umezawa, K. et al., Drugs Exptl. Clin. Res. 22: 35-40 (1996)).

It is also known that conophylline induces insulin production of pancreatic acinar carcinoma AR42 J-B13 cells. (The Book of Abstracts (01-21) of the 45th Annual Meeting of the Japan Diabetes Society held in Tokyo, May 18, 2002). However, these cancer cells did not release insulin into culture medium.

The object of the present invention is to provide agents capable of inducing insulin production and/or secretion of non-neoplastic cells derived from the pancreas.

DISCLOSURE OF THE INVENTION

The present inventors have intensively studied to solve the above-mentioned problems and, as a result, found that vinca alkaloids markedly induce differentiation of normal pancreatic cells into insulin-producing and -releasing cells in vitro. Thus, the present invention has been accomplished.

The following summarizes the present invention.

-   1. An agent for increasing insulin-producing ability of a     non-neoplastic cell derived from the pancreas, containing a vinca     alkaloid or its pharmacologically acceptable salt as an active     ingredient. A preferred example of the aforementioned vinca alkaloid     is conophylline. The agent preferably further contains nicotinamide,     or nicotinamide and hepatocyte growth factor (HGF). -   2. An agent for increasing insulin-secreting ability of a     non-neoplastic cell derived from the pancreas, containing a vinca     alkaloid or its pharmacologically acceptable salt and nicotinamide     as active ingredients. A preferred example of the aforementioned     vinca alkaloid is conophylline. The agent preferably further     contains hepatocyte growth factor (HGF). -   3. A preventive and/or a therapeutic agent for a disease associated     with lack of insulin, containing a vinca alkaloid or its     pharmacologically acceptable salt as an active ingredient. A     preferred example of the aforementioned vinca alkaloid is     conophylline. The disease associated with lack of insulin is     selected from the group consisting of diabetes, arteriosclerosis,     and a complication resulting from these diseases. The preventive     and/or the therapeutic agent for a disease associated with lack of     insulin preferably further contains nicotinamide, or nicotinamide     and hepatocyte growth factor (HGF). -   4. A blood glucose level-lowering agent containing a vinca alkaloid     or its pharmacologically acceptable salt as an active ingredient. A     preferred example of the aforementioned vinca alkaloid is     conophylline. The blood glucose level-lowering agent preferably     further contains nicotinamide, or nicotinamide and hepatocyte growth     factor (HGF) -   5. An agent for inducing differentiation from a non-neoplastic cell     derived from the pancreas into an insulin-producing cell, containing     a vinca alkaloid or its pharmacologically acceptable salt as an     active ingredient. A preferred example of the aforementioned vinca     alkaloid is conophylline. The agent for inducing differentiation     preferably further contains nicotinamide, or nicotinamide and     hepatocyte growth factor (HGF). -   6. An agent for inducing differentiation from a non-neoplastic cell     derived from the pancreas into an insulin-secreting cell, containing     a vinca alkaloid or its pharmacologically acceptable salt and     nicotinamide as active ingredients. A preferred example of the     aforementioned vinca alkaloid is conophylline. The agent for     inducing differentiation preferably further contains nicotinamide,     or nicotinamide and hepatocyte growth factor (HGF). -   7. An agent for promoting induction of differentiation from a     non-neoplastic cell derived from the pancreas into an     insulin-producing cell, consisting of a vinca alkaloid or its     pharmacologically acceptable salt. A preferred example of the     aforementioned vinca alkaloid is conophylline. -   8. A method for inducing differentiation of a non-neoplastic cell,     in which a vinca alkaloid or its pharmacologically acceptable salt     is added when the non-neoplastic cell derived from the pancreas is     cultured. In this manner, by culturing non-neoplastic cells derived     from the pancreas in the presence of a vinca alkaloid or its     pharmacologically acceptable salt, the non-neoplastic cell derived     from the pancreas differentiate into an insulin-producing cell or an     insulin-secreting cell. In induction of differentiation of a     non-neoplastic cell derived from the pancreas, nicotinamide, or     nicotinamide and hepatocyte growth factor (HGF) are preferably used.     A preferred example of the aforementioned vinca alkaloid is     conophylline. -   9. A method for increasing insulin-producing ability of a     non-neoplastic cell derived from the pancreas, in which a vinca     alkaloid or its pharmacologically acceptable salt is added when the     non-neoplastic cell derived from the pancreas is cultured. A     preferred example of the aforementioned vinca alkaloid is     conophylline. To increase insulin-producing ability of the     non-neoplastic cell derived from the pancreas, nicotinamide, or     nicotinamide and hepatocyte growth factor (HGF) are preferably used. -   10. A method for increasing insulin-secreting ability of a     non-neoplastic cell derived from the pancreas, in which a vinca     alkaloid or its pharmacologically acceptable salt is added when the     non-neoplastic cell derived from the pancreas is cultured. A     preferred example of the aforementioned vinca alkaloid is     conophylline. To increase insulin-secreting ability of the     non-neoplastic cell derived from the pancreas, it is preferable to     use nicotinamide, or nicotinamide and hepatocyte growth factor     (HGF). -   11. A method for producing a pancreas-derived non-neoplastic cell     whose insulin-producing and/or secreting abilities have been     increased, which includes culturing the non-neoplastic cells derived     from the pancreas in the presence of a vinca alkaloid or its     pharmacologically acceptable salt. In this manner, by culturing a     non-neoplastic cell derived from the pancreas in the presence of     vinca alkaloid or its pharmacologically acceptable salt, it is     possible to produce a pancreas-derived non-neoplastic cell whose     insulin-producing ability has been increased (an insulin-producing     cell)or a pancreas-derived non-neoplastic cell whose     insulin-secreting ability has been increased (an insulin-secreting     cell) In induction of differentiation of a non-neoplastic cell     derived from the pancreas, it is preferable to use nicotinamide, or     nicotinamide and hepatocyte growth factor (HGF). A preferred example     of the aforementioned vinca alkaloid is conophylline. -   12. A method for producing insulin, which includes culturing a     non-neoplastic cell derived from the pancreas in the presence of     vinca alkaloid or its pharmacologically acceptable salt and     nicotinamide and isolating and purifying insulin from a culture (the     cultured cell or a medium). A preferred example of the     aforementioned vinca alkaloid is conophylline. -   13. A method for producing insulin, which includes culturing a     non-neoplastic cell derived from the pancreas in the presence of     conophylline or its pharmacologically acceptable salt, nicotinamide,     and hepatocyte growth factor (HGF) and isolating and purifying     insulin from the cultured cell or a medium. A preferred example of     the aforementioned vinca alkaloid is conophylline. -   14. A pancreas-derived non-neoplastic cell (an insulin-producing     cell or an insulin-secreting cell) that has been induced to     differentiate by the method of 8 described above. -   15. A pancreas-derived non-neoplastic cell whose insulin-producing     ability has been increased by the method of 9 described above. -   16. A pancreas-derived non-neoplastic cell whose insulin-secreting     ability has been increased by the method of 10 described above. -   17. A preventive and/or a therapeutic method for a disease     associated with lack of insulin, which uses a vinca alkaloid or its     pharmacologically acceptable salt. A preferred example of the     aforementioned vinca alkaloid is conophylline. The disease     associated with lack of insulin is selected from the group     consisting of diabetes, arteriosclerosis, and a complication     resulting from these diseases. The preventive and/or the therapeutic     agent for a disease associated with lack of insulin preferably     further contains nicotinamide, or nicotinamide and hepatocyte growth     factor (HGF). -   18. A preventive and/or a therapeutic method for a disease     associated with lack of insulin, which includes culturing a     non-neoplastic cell derived from the pancreas in the presence of a     vinca alkaloid or its pharmacologically acceptable salt and     nicotinamide; and using the cultured non-neoplastic cell derived     from the pancreas. Alternatively, the method may include culturing a     non-neoplastic cell derived from the pancreas in the presence of a     vinca alkaloid or its pharmacologically acceptable salt,     nicotinamide, and hepatocyte growth factor (HGF); and using the     cultured non-neoplastic cell derived from the pancreas. A preferred     example of the aforementioned vinca alkaloid is conophylline. The     disease associated with lack of insulin is selected from the group     consisting of diabetes, arteriosclerosis, and a complication     resulting from these diseases.

“Vinca alkaloids” as used herein refer to vinblastine and vincristine isolated from Vincarosea, an Apocynaceae family plant, and to alkaloids containing the backbone represented by the following structural formula:

It should be noted that alkaloids refer to cyclic compounds produced by plants with a nitrogen atom (N) in the ring. Specific examples of vinca alkaloids include, but not limited to vinblastine, vincristine, conophylline, conophyllidine, conofoline, conophyllinine, taberhanine, pachysiphine etc., as shown in FIG. 1.

“Non-neoplastic cells derived from the pancreas” as used herein refer to cells without tumorigenicity that are derived from the pancreas of individual organisms. Such cells include those harvested from the pancreas of organisms and those cultivated from the harvested cells (i.e., cultured cells). Cultured cells include both primary cultured cells and successively transferred cells.

“To increase insulin-producing ability and/or -secreting abilities of cells” is a concept including both causing cells that do not have insulin-producing and/or -secreting abilities to acquire insulin-producing and/or -secreting abilities and causing cells that have insulin-producing and/or -secreting abilities to enhance their insulin-producing and/or -secretion abilities.

“To differentiate into β cells” as used herein means that progenitor cells of β cells come to produce and secrete insulin.

As mentioned earlier, it is known that conophylline, a kind of vinca alkaloid, induces insulin production of pancreatic acinar carcinoma AR42 J-B13 cells, but the AR42 cells were found to be incapable of releasing insulin out of cells, though they do produce insulin. It was unpredictable that, under conditions in which only such weak effects are known, a vinca alkaloid induces insulin production, and further, can even release insulin out of cells when non-neoplastic cells derived from the pancreas were used instead.

Activin, which is capable of inducing AR42J cells to produce insulin, does not exhibit the effect on porcine pancreatic cells. To induce ES cells to produce insulin, many factors including leukocyte activating factor (LAF) as well as many processes are required. The conditions under which cells are induced to differentiate are different depending on the individual cell type. For this reason, even those skilled in the art could not predict that a vinca alkaloid increases insulin production of non-neoplastic cells derived from pancreas and induces insulin to be secreted out of the cells.

Furthermore, since AR42J cells were cancer cells, they could not be used for regenerative medicine from the viewpoint of safety even if their insulin-producing ability was increased. The technique of increasing insulin-producing and -secreting abilities of non-neoplastic cells derived from the pancreas has been established by the present invention, which has made it possible to prepare large amounts of cells available for regenerative medicine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the chemical structural formulae of several compounds belonging to the vinca alkaloid family.

FIG. 2 shows the results of immunostaining of fetal porcine pancreatic cells cultured in media to which the following were added for three weeks: vehicle (1) ; only nicotinamide (10 mM) (2); nicotinamide (10 mM) and HGF (10 ng/ml) (4);only conophylline (0.1 μg/ml) (5); conophylline (0.1 μg/ml) and HGF (10 ng/ml) (7); conophylline (0.1 μg/ml), nicotinamide (10 mM), and HGF (10 ng/ml) (8). In the figure, N and CNP denote nicotinamide and conophylline, respectively.

FIG. 3 shows the results of ELISA measurement of the amount of insulin produced by fetal porcine pancreatic cells cultured in media to which the following were added: vehicle (white circle); nicotinamide and HGF(white triangle); only conophylline (black circle); conophylline, nicotinamide, and HGF (black triangle). In the figure, N and CNP denote nicotinamide and conophylline, respectively.

FIG. 4 shows the effect of conophylline on blood glucose levels of streptozotocin-administered rats.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention accomplished based on the above-described findings are hereinafter described in detail by giving Examples. Unless otherwise explained, methods described in standard sets of protocols such as J. Sambrook and E. F. Fritsch & T. Maniatis (Ed.),“Molecular Cloning, a Laboratory Manual (3rd edition), Cold Spring Harbor Press and Cold Spring Harbor, N.Y. (2001); and F. M. Ausubel, R. Brent, R. E. Kingston, D. D. Moore, J. G. Seidman, J. A. Smith, and K. Struhl (Ed.), “Current Protocols in Molecular Biology,” John Wiley & Sons Ltd., or alternatively, modified/changed methods from these are used. When using commercial reagent kits and measuring apparatus, unless otherwise explained, attached protocols to them are used.

The objective, characteristics, and advantages of the present invention as well as the idea thereof will be apparent to those skilled in the art from the descriptions given herein. It is to be understood that the embodiments and specific examples of the invention described hereinbelow are to be taken as preferred examples of the present invention. These descriptions are for illustrative and explanatory purposes only and are not intended to limit the invention to these embodiments or examples. It is further apparent to those skilled in the art that various changes and modifications may be made based on the descriptions given herein within the intent and scope of the present invention disclosed herein.

One aspect of the present invention is hereinafter explained in detail.

1. Manufacture of Vinca Alkaloids and Their Salt

The chemical structural formulae of some compounds belonging to the vinca alkaloid family are shown in FIG. 1.

Vinblastine and vincristine can be isolated and purified from Vinca rosea Linn by the method described in Neuss N, Gorman M, Hargrove W, et al., & Manning R E (1964) J. Am. Chem. Soc. 86: 1440-1442,

Conophylline can be isolated and purified from leaves of Ervatamia microphylla, an Apocynaceae family plant, in the manner as will be described later in Production example 1 (a method modified from Umezawa, K. et al. Anticancer Res. 14: 2413-2418 (1994)). About 4 kg of Ervatamia microphylla leaves yields about 500 mg of conophylline crystals.

Conophyllidine can be prepared from leaves of Ervatamia microphillae in the same manner as conophylline (Kam, T. S. et al. J. Nat. Prod. 56: 1865-1871 (1993)).

Conofoline and pachysiphine can be prepared by the methods described in Kam T S, Anuradha S. Alkaloids from Tabernaemontana divaricata, and Phytochemistry (1995) 40: 313-6.

Conophyllinine and taberhanine can be prepared by the methods described in Kam T S, Pang H S, Lim T M, Biologically active indole and bisindole alkaloids from Tabernaemontana divaricata. Org. Biomol. Chem. (2003) 21; 1(8): 1292-7.

Examples of salts of vinca alkaloids include hydrochlorides and sulphates, which are pharmacologically acceptable. These salts can be produce by known methods.

2. Induction of Insulin Production in Non-Neoplastic Cells Derived from the Pancreas by Vinca Alkaloids and Their Salts

First, non-neoplastic cells derived from the pancreas are prepared. Non-neoplastic cells derived from the pancreas may be derived from mammals. Such mammals include primates, such as humans and monkeys, as well as non-primates, such as pigs, cattle, dogs, and rats. Cells may be derived from healthy animals or from patients who need treatment. Patients are not limited to humans; they may be unhealthy non-human animals. When non-neoplastic cells derived from a healthy animal are used, preferred animals are fetuses and neonates (for example, in the case of pigs, neonatal pigs within 3 days of birth) Non-neoplastic cells may be exocrine cells or endocrine cells, but endocrine cells are preferred. Further, among endocrine cells, β cells and their progenitor cells are more preferred.

Isolation of non-neoplastic cells from the pancreas of healthy mammalian animals may be performed, for example, as follows: The pancreas is removed from a mammal and connective tissue is detached. The pancreas is dissected, buffer is added, and the mixture is stirred. After stirring, the supernatant is discarded, an enzyme Liberase is added, and the mixture is stirred again. Subsequently, a cycle of centrifugation, discarding of the supernatant, and addition of PBS is repeated. Cells are suspended with PBS and this cell suspension is overlaid on Histopaque, followed by centrifugation. Since pancreatic endocrine cells forms a belt-like white layer at the interface between cell suspension and Histopaque, this layer is harvested. The sample is centrifuged and the supernatant is discarded. The cells is suspended in medium and transferred to the culture chamber to be incubated. Subsequently, spheroids (loose cell aggregates) are formed by stirring for an appropriate time, followed by incubation. Cells detached from the chamber and floating in the medium are used for the subsequent operations.

The cells floating in the culture chamber are transferred to the centrifuge tube, which is let to stand still until spheroids have sunk to the bottom. Then the supernatant is discarded and medium was added, followed by light shaking. The tube is let to stand still and the spheroids are allowed to settle down to the bottom. After this operation is repeated 2 or 3 times, the cell lysate is centrifuged and the supernatant is discarded. The residual cells are cultured under the condition of 5% CO₂ and 37° C. in medium supplemented with a vinca alkaloid or its pharmacologically acceptable salt. The culture may be stationary culture. Examples of suitable media include RPMI medium etc. It is also more preferable to add nicotinamide and hepatocyte growth factor (HGF) in addition to a vinca alkaloid or its pharmacologically acceptable salt. The medium may be changed every 4 to 7 days and the culture is incubated for 7 to 35 days. The morphology of the cells may be examined at suitable time intervals during the incubation period. Further, when the medium is changed, the culture solution may be recovered and subjected to the measurement of the insulin amount in the medium.

The methods for separating and culturing cells described above can also be applied when non-neoplastic cells derived from patients' pancreas are prepared. It should be noted that, to obtain non-neoplastic cells derived from patients' pancreas, a method is suggested in which tissue fragments are harvested from patients' pancreas so that non-neoplastic cells are isolated from these tissue fragments by the above-described methods.

As thus far described, by culturing non-neoplastic cells derived from the pancreas in the presence of a vinca alkaloid or its salt, differentiation of non-neoplastic cells derived from the pancreas can be induced. Preferably, non-neoplastic cells derived from the pancreas can be induced to differentiate into insulin-producing and -releasing cells (e.g., β cells). Furthermore, insulin-producing and/or -secreting abilities of normal pancreatic cells can be increased. Furthermore, by culturing non-neoplastic cells derived from the pancreas in the presence of a vinca alkaloid or its salt, insulin can be isolated and purified from cultures (cultured cells or a medium) by known methods.

The pancreas-derived non-neoplastic cells whose insulin-producing and/or -secreting abilities have been increased by culturing in the presence of a vinca alkaloid or its salt are capable of producing 10 ng or more, preferably 25 ng or more, and more preferably 55 ng or more in 1 ml of medium when they were cultured at the concentration of 2.5×10⁵ cells per 1 ml of medium for 7 to 35 days.

As mentioned earlier, porcine pancreatic cells are expected to be used in regenerative therapy for diabetes because of their ease of availability, immunological properties, etc. The method for collecting large amounts of cells to induce them to differentiate into insulin-producing and -releasing cells to a sufficient degree has never been known in any cell system.

The technique according to the present invention makes it possible to induce large amounts of cells to differentiate into insulin-producing and -releasing cells to a sufficient degree. Accordingly, insulin-producing and -releasing cells obtained by the methods according to the present invention can be used in regenerative medicine for diabetes.

Insulin-producing and -releasing cells obtained by the methods according to the present invention may be suspended in a solution and/or embedded in a support matrix and then administered to subjects. The solution in which insulin-producing and -releasing cells are suspended may be a pharmacologically acceptable carrier and diluent, such as saline, a buffer solution, etc. To the solution, a preservative (e.g., p-hydroxybenzoic acid ester, chlorobutanol, thiromesal, etc.) and a stabilizer (e.g., L-arcorbic acid, etc.) may be added. After insulin-producing and -releasing cells are suspended in the solution, they may be subjected to a sterilization treatment. A support matrix in which insulin-producing and -releasing cells are embedded may be a matrix that is recipient-compatible and that degrades into a product not harmful to the recipient. Materials for the matrix may include natural polymers, synthetic polymers, etc. Examples of natural polymers include collagen, gelatin, etc. Examples of synthetic polymers include polyglycolic acid, polylactic acid, etc. The matrix can be in the form of, but not limited to, film, sheet, particle, paste, etc.

3. Agents and Drugs Based on Vinca Alkaloids

Vinca alkaloids and their pharmacologically acceptable salts can increase insulin-producing and/or -secreting abilities of non-neoplastic cells derived from the pancreas. Further, vinca alkaloids and their pharmacologically acceptable salts can also decrease blood glucose levels. Therefore, these compounds may be administered to human and other animals as drugs (e.g., therapeutic agents for diabetes) or may be used as reagents in experiments. These compounds may be used alone or in combination with other agents (e.g., other therapeutic agents for diabetes). It should be noted that, when a vinca alkaloid has been administered to an animal, its effect is likely to have been enhanced by taking advantage of endogenous nicotinamide and/or an endogenous hepatocyte growth factor (HGF); thus, in administering a vinca alkaloid, nicotinamide and/or hepatocyte growth factor (HGF) may be simultaneously administered.

When administered to humans, a vinca alkaloid or its pharmacologically acceptable salt may be administered orally. The dosage is, for example, 0.1 to 10 mg/kg bw daily in a single dose or divided doses. However, the amount of a dose and number of administration can be suitably changed depending on the symptoms, age, dosage regimen, etc.

Vinca alkaloids and their pharmacologically acceptable salts may be administered orally in preparations, such as tablets, capsules, granule, powder, syrups, etc. Alternatively, they may be administered parenterally by intraperitoneal or intravenous injection in preparations such as injectable formulations, suppositories, etc. The content of a vinca alkaloid or its pharmacologically acceptable salt (active ingredient) in a preparation can vary between 1 to 90% by weight. For example, when the preparation is in the form of a tablet, a capsule, a granule, a powder, etc. the content of an active ingredient is preferably 5 to 80% by weight. In the case of a liquid preparation such as syrup, the content of an active ingredient is preferably 1 to 30% by weight. In addition, in the case of an injectable preparation for parenteral administration, the content of an active ingredient is preferably 1 to 10% by weight.

Vinca alkaloids and their pharmacologically acceptable salts are formulated by known methods using the following formulation additives: excipients (sugars such as lactose, sucrose, glucose, and mannitol; starches such as potato, wheat, and corn; inorganic substances such as calcium carbonate, calcium sulfate, and sodium hydrocarbonate; cellulose crystal; etc.), binders (starch-paste liquid, gum arabic, gelatin, sodium arginate, methylcellulose, ethylcellulose, polyvinylpyrrolidone, polyvinyl alcohol, hydroxypropylcellulose, carmellose, etc.), lubricants (magnesium stearate, talc, hydrogenerated vegetable oil, macrogol, and silicone oil), disintegrators (starch, agar, gelatin powder, cellulose crystal, sodium carboxymethylcellulose, calcium carboxymethylcellulose, calcium carbonate, sodium hydrocarbonate, sodium arginate, etc.), correctives (lactose, sucrose, glucose, mannitol, fragrant essential oils, etc.), solvents (water for injection, sterile purified water, sesame oil, soybean oil, corn oil, olive oil, cottonseed oil, etc.), stabilizers (inert gases such as nitrogen and carbon dioxide; chelating agents such as EDTA and thioglycolic acid; reducing substances such as sodium bissulfite, sodium thiosulfate, L-ascorbic acid, and rongalite; etc.), preservatives (paraoxybenzoic acid, chlorobutanol, benzyl alcohol, phenol, benzalkonium chloride, etc.),detergents (hydrogenated castor oil, polysorbates 80 and 20, etc.), buffers (sodium salts of citric acid, acetic acid, and phosphoric acid; boric acid; etc.), diluents, etc.

Vinca alkaloids and their pharmacologically acceptable salts can be used to prevent and/or treat diseases (e.g., diabetes and arteriosclerosis) associated with lack of insulin. Vinca alkaloids and their pharmacologically acceptable salts can also be used in studies of insulin production and/or secretion of pancreatic cells. Vinca alkaloids and their pharmacologically acceptable salt can further be used for blood glucose level-lowering agents as well as for therapeutic agents for complications resulting from prolonged high blood glucose levels, such as retinopathy of the eyes, nephropathy, neuropathy, gangrene, arteriosclerosis, etc.

Hereinafter, the present invention will be explained in more detail with reference to Production examples and Experiment examples. These Production examples and Experiment examples are for explanatory purposes only and are not intended in any way to limit the scope of the invention.

The materials used in the example and their suppliers are as follows.

-   Neonatal pigs: Takayama Pig Farm -   Roswell Park Memorial Institute (RPMI) medium: Invitrogen -   Nicotinamide: Sigma Chemical Science (Sigma) -   Fetal bovine serum (FBS): Sigma -   Phosphate buffered saline (PBS) -   Histopaque: Sigma -   Hepatocyte growth factor (HGF): Sigma Chemical Science -   DMEM: Nissui Pharmaceutical Co., Ltd. -   HEPES: Sigma -   Kanamycin: Sigma -   Glutamine: Sigma -   Penicillin G: Sigma -   Trypsin: Wako -   EDTA: Kanto Chemical Co., Inc. -   PBS⁻ for fluorescent antibodies -   Bovine serum albmine (BSA): Sigma -   Anti-insulin antibody: Biogenesis -   Cy3-conjugated anti-guinea pig antibody: Jackson -   ImmunoResearch Laboratories, Inc. (West Grove, Pa.) -   Activin A: R&D Systems,Inc.(Minneapolis, Mo.) -   Hoechst 33258: Polysciences, Inc.

EXAMPLE 1 Production Example 1 Preparation of Conophylline

Conophylline was isolated and purified from leaves of Ervatamia microphylla, an Apocynaceae family plant, (harvested in Khon Khen, Thailand) in the following manner.

Active substance was extracted from about 4 kg of Ervatamia micorophylla leaves with 100 L of chloroform to afford about 130 g of oily substance. This oily substance was chromatographed on a silica gel column (purification was performed by a total of 5 rounds of column chromatography using about 500 g of silica gel), eluting sequentially with chloroform:methanol (40:1 and 20:1). Subsequently, using morphological changes of K-ras-NRK cells as an activity marker, the fractions exhibiting this biological activity were recovered. The crude purified product obtained (about 40 g) was chromatographed on a silica gel column with n-hexane:ethyl acetate (1:2 and 0:1) (using about 500 g of silica gel; purchased from Merck Co.) to afford 1.5 g of active fractions. The active fractions were then chromatographed on a silica gel column (using 150 g of silica gel) with n-hexane:ethyl acetate:chloroform (9:3:1 and 6:3:1), active fractions were recovered, and concentrated to afford about 500 mg of crystals. The resulting conophylline was confirmed by mass spectrometry and NMR spectrometry comparing its data with the literature data (Umezawa, K. et al., Anticancer Res. 14: 2413-2418 (1994)). The solvents used were purchased from Kanto Chemical Co., Inc.

EXAMPLE 2 Experimental Examples I and II

1. Methods

Neonatal pigs within 72 hours of birth were obtained from the (Takayama) pig farm. The whole pancreas (ventral and dorsal pancreas) was removed under general anesthesia immediately after animals were brought to the operating room. After elimination of connective tissue covering the removed pancreas and blood adhering to it, the pancreas was transferred to a 10 ml beaker and dissected into small pieces with ophthalmic scissors. The dissected pieces were transferred to a 100 ml conical flask, to which 50 to 60 ml of phosphate buffered saline (PBS) was added. After a 3 min rotation at 110 rpm on a low speed stirrer, the mixture was allowed to stand still and the supernatant was discarded. Then, 40 mL of phosphate buffered saline containing Liberase PI (Roche) at a concentration of 2.5 mg/ml was added. After an 8 min rotation at 110 rpm on a low speed stirrer, the mixture was allowed to stand still and the supernatant containing the cells was collected. The operation was repeated 5 times. The supernatant collected was centrifuged at 1200 rpm for 5 min. to collect cells. The cells collected in the centrifugal sedimentum was suspended in 25 to 50 ml of PBS, 25 ml of cell suspension was overlaid gently on 10 ml of Histopaque 1077 (Sigma), followed by centrifugation at 1800 rpm for 10 min. Pancreatic (endocrine) cells form a band-like white layer at the interface between cell suspension and Histopaque (cell separation and purification methods)

Cells present at the interface are recovered with a Pasteur pipette, suspended in RPMI 1640 supplemented with 10 mM Nicotinamide and 10% heat-inactivated FBS, collected by centrifugation at 1200 rpm for 5 min. These cells were resuspended in the same medium and then subjected to stationary culture in a 75 ml culture flask (5% CO₂ incubator, 37° C.) for a whole day and night.

Culture Conditions:

Cells floating in the flask were removed, and cells adhering to the bottom were detached with EDTA-Trypsin and collected. Cells were suspended in each of media (groups 1 to 8) and stationary culture was performed by plating cells (1.25×10³ cells/ml) in culture chambers (2 ml each; 5% CO₂-incubator, 37° C.).

Media Group 1: RPMI 1640 with 10% FBS (Control)

2: Control+10 mM nicotinamide

3: Control+10 ng/ml HGF

4: Control+0.1 μg/ml conophylline

5: 2+3

6: 2+4

7: 3+4

8: 2+3+4

The culture medium was exchanged every four days and the observation was made for three weeks, during which time the morphology of cells was observed every week and the appearance of pancreatic β-cells was confirmed by immunofluorescence using peroxidase (Experiment example 1). Coloration was performed using 3-amino-9-ethyl carbazole (AEC; 0.75 mg/ml) as a substrate. In addition, the medium was recovered every time it was exchanged (every four days) for measurement of the amount of insulin secreted into the medium by ELISA (Experiment example II).

2. Results

FIG. 2 shows the results of Example 1 It has been reported that nicotinamide (Akiyama, T. et al., Proc. Natl. Acad. Sci. USA 98: 48-53 (2001)) and HGF (Ocana, A. G. et al., J. Biol. Chem. 275: 1226-1232 (2000)) promote differentiation of insulin-producing cells in the limited experimental systems, but their effects are weak. As shown in FIG. 2, three weeks later, only a few insulin-producing cells colored in red were seen in vehicle (1), only nicotinamide (10 mM) (2), nicotinamide and HGF (10 ng/ml) (4), only conophylline (0.1 μg/ml) (5), and conophylline and HGF (7). In the triple mixture of nicotinamide, HGF, and conophylline (8), however, the number of insulin-producing cells colored markedly in red increased. It should be noted that the mixture of nicotinamide and conophylline (6) produced a smaller number of insulin-producing cells than the aforementioned triple mixture the mixture (6) did; however, nicotinamide-conophylline mixture had a marked increase in that number, compared with the others (not shown in the figure).

FIG. 3 shows the results of Example II. As indicated in FIG. 3, nicotinamide combined with either HGF or conophylline cultured for 8 to 20 days was able to produce some amount of insulin in the medium. Furthermore, nicotinamide combined with HGF and conophylline had a marked increased in the amount of insulin release, compared with other combinations or alone.

Summary

To date, there have been no techniques for inducing differentiation of insulin-producing cells in pancreatic cells of neonatal pigs. It has been revealed that the combination of nicotinamide, HGF, and conophylline dramatically increases the proportion of insulin-producing cells, thereby resulting in a large amount of insulin release as well. Since the neonatal porcine pancreas can be supplied in large amounts, it will be possible to prepare in large amounts implantable cells that release enough insulin. It is thought that this technique enables regenerative therapy, which is expected for diabetes in the future.

Further, conophyllidine, like conophylline, has been confirmed to induce morphological changes involved in insulin production of pancreatic acinar carcinoma AR42J cells, suggesting that conophyllidine, like conophylline, has the effect of increasing insulin-producing and/or -secreting abilities of non-neoplastic cells derived from the pancreas.

EXAMPLE 3 Comparative Example 1 Effect in Which Conophylline Induces Differentiation of Rat Pancreatic Acinar Carcinoma AR42 J-B13 Cells Into Insulin-Producing Cells

1. Methods

Cell Culture

DMEM was sterilized by filtration after its pH was adjusted to 7.4 in the presence of 20 mM HEPES-NaOH. AR42J-B13 cells (endowed by Dr. Itaru Kojima, Institute for Cellular and Molecular Regulation, Gunma University) a highly sensitive subclone of AR42J, were cultured at 37° C. in a 5% CO₂ incubator with 20 ml of culture medium DMEM supplemented with 100 mg/l kanamycin, 0.6 g/l glutamine, 100 unit/ml penicillin G, 5 mM NaHCO₃, and 10% FBS. To prevent transformation due to a high density of the cells and to retain differentiation ability of the cells, the cells were transferred every 2 to 3 days to maintain 2.5% to 5% of confluency. The cell transfer was performed as follows: After the medium was removed, the cells were washed twice in PBS⁻ (Ca²⁺, Mg²⁺-free PBS; 8 g/l, NaCl, 0.2 g/l KCl, 0.916 g/Na₂HPO₄, 0.2 g/l KH₂PO₄). Subsequently, the cells were detached using 2 ml of trypsin-EDTA solution, and then trypsin was inactivated by addition of 8 ml of the medium. Subsequently, the cell were sedimented by centrifugation at 1000 rpm for 5 min, trypsin was removed, 10 ml of fresh medium was added, and transferred to be 2.5% to 5% of confluency. Cells were cryopreserved under the condition of 7.5% dimethyl sulfoxide (DMSO).

Cells that had been prepared at a density of 4×10⁵ cells/ml were plated at 500 μl per well on 24-well plates, followed by incubation at 37° C. in a 5% CO₂ incubator. The next day, either 0.1-0.3 μg/ml conophylline alone or 0.1 μg/ml conophylline plus 100 pM HGF was added. After incubation for an appropriate time at 37° C. in 5% CO₂, the medium was removed to a 1.5 ml Eppendorf tube, cells were washed once in 200 μl of PBS⁻, and then 200 μl of fresh PBS⁻ was added. The morphology of the viable cells was observed and photographed at 150× magnification with a camera linked to the microscope. Subsequently, cells were detached with trypsin and all the solution was transferred to the aforementioned Eppendorf tube for trypan blue exclusion test. Further, the photograph was enlarged 2.5 times and a morphological change was defined as having occurred when the full length of a cell in the diameter became 1.5 times; thus, the rates of morphological changes were determined.

Immunofluorescence

Cells that had been prepared at a density of 2×10⁵ cells/ml were plated at 500 μl per well on 8-well plates, followed by addition of either 0.1 μg/ml conophylline or 0.1 μg/ml conophylline plus 100 pM HGF. Subsequently, the cells were incubated at 37° C. in a 5% CO₂ incubator for 72 hours to differentiate. After the medium was removed, the cells were washed once with PBS⁻ for fluorescent antibodies (8 g/l NaCl, 50.45 g/l NaH₂PO₄.2H₂O, 1.28 g/l Na₂HPO₄) and fixed with 3% formaldehyde at 4° C. overnight (or at room temperature for 30 min). Next, the cells were washed twice with PBS⁻ for fluorescent antibodies and blocked by adding 1 ml of 1% BSA solution (a solution of PBS⁻ for fluorescent antibodies) per well, followed by incubation at room temperature for 1 hour. To quench with 50 mM glycine (a solution of PBS⁻ for fluorescent antibodies), cells were incubated for 5 min, followed by washing 3 times. Next, the solution in the plastic wells was removed, 50 μl per well of alpha-insulin antibody diluted 100-fold with a 10-fold diluted blocking buffer was placed taking care not to allow cells to dry, and the plates were allowed to stand still at room temperature for 1 hour. Here, a well of cells induced to differentiate with 2 nM activin A and 100 pM HGF was prepared and preserved without primary antibody for the purpose of comparing the influence of the nonspecific binding of the secondary antibody. Next, slides were transferred to the chamber and washed three times with PBS⁻ for fluorescent antibodies for 5 min while shaking on a shaker. Next, Hoechst 33258 was added to Cy3-conjugated anti-guinea pig antibody diluted 100-fold with a 10-fold diluted blocking solution at a 1:100 dilution, and the antibody was overlaid as was the primary antibody. The slides were shielded from light with aluminum foil, allowed to stand still at room temperature for 1 hour and then placed in the shielded chamber, followed by washing three times for 10 min with TNT buffer (0.1 M Tris-HCl, 0.15 MNaCl, 0.05% Tween 20; pH 7.5) under light shielding on the shaker. The slides were overlaid with 50% glycerol in PBS⁻, covered with coverslips, and photographed under the microscope.

2. Results

When conophylline was used alone and in combination with HGF, process outgrowth such as that seen in nerve cells was concentration-dependently induced at concentrations of 0.1 to 0.3 μg/ml. Further, combination with HGF slightly enhanced cell death, thereby increasing the rates of morphological changes.

The results of the immunofluorescence revealed the following: After 72 hours, when 100 pM HGF was used alone, no red coloration indicating insulin was observed in cells. When 0.1 μg/ml conophylline and 100 pM HGF were used in combination, however, red coloration of insulin was observed in the cytoplasm excluding the nucleus. Further, the coloration was seen scattered as if insulin was confined in granules in the cytoplasm. No insulin coloration was observed in the vicinity of the cell membrane involved in insulin release. Meanwhile, when 2 nM activin A and 100 pM HGF were used in combination, red coloration of insulin was observed in granules as in combination of conophylline and HGF, but its localization was different: the red coloration was observed along the axis of the process split into two, with some accumulation at the tips of the neurites.

In addition, quantification of insulin secretion of the differentiated cells was attempted using the ELISA method, but the secretion was found to be below the detection level.

Summary

In conclusion, it was revealed that conophylline is capable of inducing morphological changes of ARJ42 cells, thereby inducing ARJ cells to produce insulin, but that conophylline is incapable of inducing insulin secretion out of cells.

EXAMPLE 4 Effect of Lowering Blood Glucose Levels in vivo By Conophylline

Example 2 revealed that conophylline has the effect of inducing pancreatic cells to produce and release insulin in vitro. To examine whether the administration of conophylline induces insulin production in vivo as well, changes in blood glucose levels caused by the administration of conophylline in vivo were measured.

Ten 1-day old Wistar rats (purchased from Japan SLC, Shizuoka, Japan) were intraperitoneally injected with streptozotocin (purchased from Wako Pure Chemical Industries, Ltd., dissolved in 0.05 mM citrate buffer (pH 4.5)) at 85 μg/g BW per rat. Streptozotocin decreases insulin production by destroying pancreatic β cells, thereby inducing diabetes. The day of streptozotocin injection was defined as day 0. Starting from the next day (day 1), five rats were injected subcutaneously with a solution (ethanol) of conophylline at 5 μg/g BW for seven consecutive days and their random blood glucose levels were measured daily. Five rats in the control group received the same volume of solvent (Control). As a result, as shown in FIG. 4, all the rats showed a remarkable increase in blood glucose levels when streptozotocin was administered, whereas the rats administered conophylline (black circle) showed an apparent decrease in blood glucose levels, compared with the control (white circle), indicating the effect of lowering blood glucose levels by conophylline (*: P<0.05, **: P<0.01 vs Control). These findings revealed that conophylline induces insulin production in vivo as well.

In addition, conophylline alone exerted an effect, as compared with the results obtained in vitro. This suggests that when conophylline has been administered into the body, endogenous nicotinamide and/or hepatocyte growth factor (HGF) have been utilized.

INDUSTRIAL APPLICABILITY

Agents capable of inducing insulin production and/or sercretion of non-neoplastic cells derived from the pancreas have been provided by the present invention.

The agents according to the present invention can induce differentiation of non-neoplastic cells derived from the pancreas. Further, the agents according to the present invention can increase insulin-producing and/or -secreting abilities of non-neoplastic cells derived from the pancreas. 

1. An agent for increasing insulin-producing ability of a non-neoplastic cell derived from the pancreas, comprising conophylline or its pharmacologically acceptable salt as an active ingredient.
 2. The agent for increasing insulin-producing ability of a non-neoplastic cell derived from the pancreas of claim 1, further comprising nicotinamide.
 3. The agent for increasing insulin-producing ability of a non-neoplastic cell derived from the pancreas of claim 1, further comprising nicotinamide and hepatocyte growth factor (HGF).
 4. An agent for increasing insulin-secreting ability of a non-neoplastic cell derived from the pancreas, comprising conophylline or its pharmacologically acceptable salt and nicotinamide as active ingredients.
 5. An agent for increasing insulin-secreting ability of a non-neoplastic cell derived from the pancreas, comprising conophylline or its pharmacologically acceptable salt, nicotinamide, and hepatocyte growth factor (HGF) as active ingredients.
 6. A preventive agent and/or a therapeutic agent for a disease associated with lack of insulin, comprising conophylline or its pharmacologically acceptable salt as an active ingredient.
 7. The preventive and/or the therapeutic agent for a disease associated with lack of insulin of claim 6, wherein the disease associated with lack of insulin is selected from the group consisting of diabetes, arteriosclerosis, and a complication resulting from these diseases.
 8. The preventive agent and/or the therapeutic agent for a disease associated with lack of insulin of claim 6, further comprising nicotinamide.
 9. The preventive agent and/or the therapeutic agent for a disease associated with lack of insulin of claim 6, further comprising nicotinamide and hepatocyte growth factor (HGF).
 10. A blood glucose level-lowering agent comprising conophylline or its pharmacologically acceptable salt as an active ingredient.
 11. The blood glucose level-lowering agent of claim 10, further comprising nicotinamide.
 12. The blood glucose level-lowering agent of claim 10, further comprising nicotinamide and hepatocyte growth factor (HGF).
 13. An agent for inducing differentiation from a non-neoplastic cell derived from the pancreas into an insulin-producing cell, comprising conophylline or its pharmacologically acceptable salt as an active ingredient.
 14. The agent for inducing differentiation of claim 13, further comprising nicotinamide.
 15. The agent for inducing differentiation of claim 13, further comprising nicotinamide and hepatocyte growth factor (HGF).
 16. An agent for inducing differentiation from a non-neoplastic cell derived from the pancreas into an insulin-secreting cell, comprising conophylline or its pharmacologically acceptable salt and nicotinamide as active ingredients.
 17. An agent for inducing differentiation from a non-neoplastic cell derived from the pancreas into an insulin-secreting cell, comprising conophylline or its pharmacologically acceptable salt, nicotinamide, and hepatocyte growth factor (HGF) as active ingredients.
 18. An agent for promoting induction of differentiation from a non-neoplastic cell derived from the pancreas into an insulin-secreting cell, consisting of conophylline or its pharmacologically acceptable salt.
 19. A method for inducing differentiation from a non-neoplastic cell derived from the pancreas into an insulin-producing cell, wherein conophylline or its pharmacologically acceptable salt is added when the non-neoplastic cell derived from the pancreas is cultured.
 20. A method for inducing differentiation from a non-neoplastic cell derived from the pancreas into an insulin-secreting cell, wherein conophylline or its pharmacologically acceptable salt and nicotinamide are added when the non-neoplastic cell derived from the pancreas is cultured.
 21. A method for inducing differentiation from a non-neoplastic cell derived from the pancreas into a insulin-secreting cell, wherein conophylline or its pharmacologically acceptable salt, nicotinamide, and hepatocyte growth factor (HGF) are added when the non-neoplastic cell derived from the pancreas is cultured.
 22. A method for increasing insulin-producing ability of a non-neoplastic cell derived from the pancreas, wherein conophylline or its pharmacologically acceptable salt is added when the non-neoplastic cell derived from the pancreas is cultured.
 23. A method for increasing insulin-secreting ability of a non-neoplastic cell derived from the pancreas, wherein conophylline or its pharmacologically acceptable salt is added when the non-neoplastic cell derived from the pancreas is cultured.
 24. A method for producing an insulin-producing cell, comprising culturing a non-neoplastic cells derived from the pancreas in the presence of conophylline or its pharmacologically acceptable salt.
 25. A method for producing an insulin-secreting cell, comprising culturing a non-neoplastic cells derived from the pancreas in the presence of conophylline or its pharmacologically acceptable salt and nicotinamide.
 26. A method for producing an insulin-secreting cell, comprising culturing a non-neoplastic cells derived from the pancreas in the presence of conophylline or its pharmacologically acceptable salt, nicotinamide, and hepatocyte growth factor (HGF).
 27. A method for producing insulin, comprising: culturing a non-neoplastic cell derived from the pancreas in the presence of conophylline or its pharmacologically acceptable salt and nicotinamide; and isolating and purifying insulin from the cultured cell or a medium.
 28. A method for producing insulin, comprising: culturing a non-neoplastic cells derived from the pancreas in the presence of conophylline or its pharmacologically acceptable salt, nicotinamide, and hepatocyte growth factor (HGF); and isolating and purifying insulin from the cultured cell or a medium.
 29. An insulin-producing cell that has been induced to differentiate by the method of claim
 19. 30. An insulin-secreting cell that has been induced to differentiate by the method of claim 20 or
 21. 31. A pancreas-derived non-neoplastic cell whose insulin-producing ability has been increased by the method of claim
 22. 32. A pancreas-derived non-neoplastic cell whose insulin-secreting ability has been increased by the method of claim
 23. 33. A preventive and/or a therapeutic method for a disease associated with lack of insulin, comprising using conophylline or its pharmacologically acceptable salt.
 34. A preventive and/or a therapeutic method for a disease associated with lack of insulin, comprising: culturing a non-neoplastic cell derived from the pancreas in the presence of conophylline or its pharmacologically acceptable salt and nicotinamide; and using the cultured non-neoplastic cell derived from the pancreas.
 35. A preventive and/or a therapeutic method for a disease associated with lack of insulin, comprising: culturing a non-neoplastic cell derived from the pancreas in the presence of conophylline or its pharmacologically acceptable salt, nicotinamide, and hepatocyte growth factor (HGF); and using the cultured non-neoplastic cell derived from the pancreas. 